I am editing a mixed media project at the moment. I downconverted and added pulldown to my 720P24 source via the BR-HD50 deck and captured anolog with decklink into the DV codec.
I'm keeping my SD60i and HD24P elements on different video tracks while I edit the offline.
Once I lock the cut, I will split off the HD elements into a new timeline, and then probably use Graeme Nattress' filter to create 24P out of 60i for the SD material. The SD24P material will then need to be scaled up to 720P and cropped to 16x9. FCP5.1 seems to do a good job of this, but if I am not happy with the results I will probably just output the DV codec back to tape and then recapture in HD and let the BR-HD50 upconvert for me to 720P.